Low viscosity noncrystalline dicyanate ester blends with prepolymers of dicyanate esters

Abstract

Low viscosity dicyanate esters are made from bisphenols wherein the bridging member between the phenyl groups is unsymmetrical. These dicyanate esters are blended with prepolymers of dicyanate esters to form low viscosity non-crystallizing resins useful in preparing composites.

I claim: 
     
       1. A curable composition comprising a blend of: (a) a dicyanate ester of a dihydric phenol having the formula: ##STR3##  wherein R and R' are difference and wherein R is H or C 1  to C 3  alkyl and R' is C 1  to C 4  alkyl, and   (b) a prepolymer of dicyanate esters of dihydric phenols different from the dicyanate ester of (a) wherein about 5 to about 50 percent of the cyanate functional groups are cyclotrimerized, wherein (a) and (b) are present in the amount of about 1 to about 99 parts by weight of (a) and about 99 to about 1 parts by weight of (b), the total weight being 100 parts.   
     
     
       2. The composition of claim 1 wherein R is hydrogen and R' is methyl. 
     
     
       3. The composition of claim 1 wherein R is methyl and R' is ethyl. 
     
     
       4. The composition of claim 1 wherein the prepolymer is a homopolymer of a dicyanate ester of dihydric phenol. 
     
     
       5. The composition of claim 1 wherein the prepolymer is a copolymer of at least two different dicyanate esters of dihydric phenols. 
     
     
       6. The composition of claim 4 wherein the prepolymer is a prepolymer of di(cyanatophenyl) ether. 
     
     
       7. The composition of claim 4 wherein the prepolymer is a prepolymer of bis(4-cyanatophenyl)-2,2-propane. 
     
     
       8. The composition of claim 4 wherein the prepolymer is a prepolymer of bis(4-cyanato-3,5-dimethylphenyl methane. 
     
     
       9. The composition of claim 5 wherein the prepolymer is a co-polymer of bis(4-cyanatophenyl)-2,2-propane and bis(4-cyanato-3,5-dimethylphenyl methane. 
     
     
       10. A curable composition comprising a blend of: (a) a dicyanate ester of a dihydric phenol having the formula: ##STR4##  wherein R and R' are different and wherein R is H or C 1  to C 3  alkyl and R' is C 1  to C 4  alkyl, and   (b) a prepolymer of dicyanate esters of dihydric phenols different from the dicyanate ester of (a) wherein about 5 to about 50 percent of the cyanate functional groups are cyclotrimerized, wherein (a) and (b) are present in the amount of about 5 to about 8 parts by weight of (a) and about 95 to about 20 parts by weight of (b), the total weight being 100 parts.   
     
     
       11. The composition of claim 10 wherein R is methyl and R' is ethyl. 
     
     
       12. The composition of claim 10 wherein R is H and R' is methyl. 
     
     
       13. The composition of claim 10 wherein about 15 to about 40 percent of the cyanate functional groups are cyclotrimerized. 
     
     
       14. The composition of claim 13 wherein the prepolymer is a homopolymer of a dicyanate ester of a dihydric phenol. 
     
     
       15. The composition of claim 14 wherein the prepolymer is a prepolymer of bis(4-cyanatophenyl)-2,2-propane. 
     
     
       16. The composition of claim 14 wherein the prepolymer is a prepolymer of bis(4-cyanato-3,5-dimethylphenyl) methane. 
     
     
       17. The composition of claim 14 wherein the prepolymer is a prepolymer of di(cyanatophenyl)ether. 
     
     
       18. The composition of claim 10 wherein the prepolymer is a copolymer of at least two different dicyanate esters of dihydric phenols. 
     
     
       19. The composition of claim 18 wherein the prepolymer is a co-prepolymer of bis(4-cyanatophenyl)-2,2-propane and bis(4-cyanato-3,5-dimethylphenyl) methane.